Boise, Idaho - The Director of the Idaho Department of Water Resources (IDWR) issued a final mid-season methodology order Thursday for Snake River ground water users, reducing the predicted shortfall to 52,600-acre feet of water to senior priority surface water users in the Eastern Snake River Plain (ESPA) region in the 2022 irrigation season.
Because of a wet and cool April and May, the IDWR methodology order’s impact was reduced from an initial prediction of a 162,600 acre-foot shortfall in April to 52,600 acre-feet in July. The Director’s order found that, among the seven members of the Surface Water Coalition, all of whom have senior surface water rights on the Snake River, the Twin Falls Canal Company and American Falls Reservoir District #2 were expected to experience material injury from ground water pumping on the ESPA.
The shortfall prediction means that IDWR will continue to curtail more than 142 ground water rights with priority dates junior to March 12, 1989 in the coming weeks, if the holders of those water rights do not come into compliance with an approved mitigation plan with a ground water district. The April order used a priority date of Dec. 25, 1979.
Currently, there are seven approved mitigation plans for the ESPA surface water delivery call. The approved plans came from the Idaho Ground Water Appropriators, Inc. (IGWA), Southwest Irrigation District, Goose Creek Irrigation District, Coalition of Cities and Water Mitigation Coalition. Those entities will not need to show how they can mitigate for projected water shortfalls, the Director’s order said.
Junior ground water users affected by the Director’s final order were sent a copy of the order on July 20.
"By law, we have to keep people with senior water rights whole, and we want to make the junior ground water pumpers aware that despite the settlement agreements between the Surface Water Coalition, IGWA, and the Participating Cities, if junior ground water pumpers are not participating in an approved mitigation plan, they could be subject to curtailment," said Mathew Weaver, Deputy Director of IDWR.
Much water litigation has resulted over conflicts between Snake River surface water users who have senior water rights under the basic principal of Idaho water law — first in time, first in right — and ground water users with junior water rights in the ESPA. Consequently, the Director of IDWR is required to issue an order at the beginning of the irrigation season, and then again in early July, determining any shortfall in water supply to senior surface water right holders, and determining the obligations of junior ground water pumpers to curtail water use or mitigate for the impact.
Gound water users who have joined an approved mitigation plan will avoid curtailment this year and in the future, and they will avoid future large-scale litigation issues related to water use in the ESPA area that could affect cities, commerce, industry, agriculture and the Southern Idaho economy, officials said.
The Director’s order requires IDWR to evaluate the water supply conditions, the needs of the senior surface water users, and the impact of junior groundwater pumping again in August or September at the court-defined “time of need.” Depending on water conditions at the time of need, IDWR will issue another order that could increase or reduce the number of curtailed water rights.